Methods and systems for helium recovery

ABSTRACT

The present invention relates generally to processes and systems for recovering helium from low helium-containing feed gases (i.e., containing less than about 10 volume % helium and more typically, less than about 5% helium by volume). The present invention more particularly relates to processes and systems for recovering helium from low helium-containing feed gases using temperature swing adsorption (TSA) systems and multiple (e.g. two) stage vacuum pressure swing adsorption (VPSA) systems. In preferred embodiments of the invention, the first stage VPSA system is configured to provide regeneration gas for the TSA system, and/or the VPSA second stage tail gas is recycled to the first stage VPSA system.

CROSS-REFERENCE TO RELATED APPLICATION

The present invention is a division of, and claims the benefit of U.S.patent application Ser. No. 12/163,461, filed Jun. 27, 2008, which isincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to processes and systems forrecovering helium from low helium-containing feed gases (i.e.,containing less than about 10 volume % helium and more typically, lessthan about 5% helium by volume). The present invention more particularlyrelates to processes and systems for recovering helium from lowhelium-containing feed gases using temperature swing adsorption (TSA)systems and multiple (e.g. two) stage vacuum pressure swing adsorption(VPSA) systems. In preferred embodiments of the invention, the firststage VPSA system is configured to provide regeneration gas for the TSAsystem, and/or the VPSA second stage tail gas is recycled to the firststage VPSA system.

BACKGROUND OF THE INVENTION

Helium is mainly produced by the radioactive decay of heavier elementssuch as uranium and thorium. The helium formed upon radioactive decaytypically percolates slowly through rock into large cavities that alsocontain reserves of natural gas. Helium diffusion from these pocketsresults in relatively low atmospheric concentration (e.g., 5 ppmv). Oncereleased from the soil or water, it is irreversibly lost in space.Consequently, helium is considered a nonrenewable resource.

In the past, pressure swing adsorption systems have been used toseparate or remove helium from helium-containing feed gases. Suchpressure swing adsorption (PSA) or vacuum pressure swing adsorption(VPSA) systems have had low helium purity and per pass helium recoverywhen using a single stage PSA or VPSA process alone to recover helium.Prior art efforts to achieve enhanced helium purity and recovery haveincluded utilizing a combination of PSA systems and membranes, or PSAand cryogenic systems, or serial arrangements of PSA or VPSA processes.In some prior art two stage VPSA systems, the same or different numberof beds are used in the stages with PSA or VPSA cycles utilizing rinsesteps and additional compression equipment(s). Such systems andprocesses can result in higher capital and/or operating costs.

Helium-containing feed gas can contain several components, e.g. a feedstream may contain large concentrations of N₂ and trace quantities ofhydrocarbons and/or other contaminants. Prior art systems that useprimarily all carbon beds to remove the contaminants in thehelium-containing feed gas result in an inefficient, uneconomical orunsustainable helium recovery system due to the degradation of carbonadsorbent and excessive use of compression equipment that are necessaryfor various steps in the helium recovery process. Given that thehelium-containing feed gas composition can vary widely, significantchallenges have existed to determine efficient adsorbent selection for acombination of adsorbates, adsorbent configuration in the adsorber, andpurity control to achieve an efficient He recovery from PSA/VPSAprocesses.

U.S. Pat. Nos. 5,089,048 and 5,080,694 to Knoblauch et al. disclose PSAprocesses for extracting helium from a relatively helium poor gasmixture, e.g., natural gas containing 2-10% helium by volume.

U.S. Pat. No. 5,542,966 to D'Amico et al. relates to pressure swingadsorption processes to recover helium from source streams of less thanabout 10 percent by volume helium and concentrate the helium to aconcentration of greater than about 98 percent by volume. Two stages ofpressure swing adsorption are used in series. The source of the heliumgas can be natural gas wells. The source gas can contain hydrocarbons,although in many instances, the primary gas other than helium will benitrogen.

U.S. Pat. No. 5,707,425 D'Amico et al. is directed to the recovery ofhelium gas from gas streams containing about 25% by volume or more ofhelium. Two PSA processes are used in a serial arrangement.

U.S. Pat. No. 5,632,803 to Stoner et al. relates to a hybridmembrane/PSA process for producing helium product streams at purities inexcess of 98% from feed stock containing from 0.5 to 5.0% helium. Themembrane is placed upstream of two PSA processes, and all of theseparation units are arranged in a serial configuration. According tothis invention, the hybrid system utilizes at least one stage ofmembrane enrichment followed by at least two stages of pressure swingadsorption.

U.S. Pat. No. 5,224,350 to Mehra relates to a system of taking asubquality nitrogen-rich natural gas stream containing more than 0.1 mol% helium to produce a rich solvent bottoms stream that is flashed twiceto produce a methane-rich gas product and a nitrogen-helium productwhich is fed to at least one membrane unit. A reject nitrogen stream anda crude helium stream are discharged from this unit. The crude heliumstream is either compressed to a pressure within the range of 200 to3,000 psia or is compressed to no more than 1,000 psia and fed to a PSAunit which produces a reject nitrogen stream and a purified heliumstream which is compressed to a pressure within the range of 200 to3,000 psia.

U.S. Pat. No. 6,630,011 B1 to Baker al. relates to a process fortreating natural gas or other methane-rich gas to remove excessnitrogen. The process relies on two-stage membrane separation, usingmethane-selective membranes for the first stage and nitrogen-selectivemembranes for the second stage.

U.S. Pat. No. 6,179,900 B1 to Behling et al. describes processes for theseparation/recovery of gases where the desired component to be separatedfrom the mixture is present in low molar concentrations and/or low tomoderate pressures. A combined membrane/PSA process is utilized for theseparation/recovery of gaseous components which are present in thestream at low pressures and/or molar contents. The membrane unit ispositioned at the upstream end of the PSA process.

U.S. Pat. No. 7,294,172 B2 to Baksh et al. discloses a highly efficientand low cost noble gas recovery system to recover and conserve valuablegas (e.g., helium) from various applications (e.g., atomizationfurnaces, plasma furnaces, sputtering, etc.). In addition, U.S. Pat. No.7,169,210 B2 to Baksh et al. relates to a control system for a heliumrecovery system.

There remains a need for improved methods and systems for heliumrecovery from low helium-containing feed gases (i.e. containing lessthan about 10% helium by volume and more typically, less than about 5%helium by volume) at high (e.g., >90%) helium recoveries, highthroughput, and improved capital and operating costs.

BRIEF SUMMARY OF THE INVENTION

As mentioned above, the present invention relates generally to processesand systems for recovering helium from low helium-containing feed gases(i.e., containing less than about 10 volume % helium and more typically,less than about 5% helium by volume). The present invention moreparticularly relates to processes and systems for recovering helium fromlow helium-containing feed gases using temperature swing adsorption(TSA) systems and multiple (e.g. two) stage vacuum pressure swingadsorption (VPSA) systems. Each stage of the VPSA systems containsmultiple (e.g. four) beds, with each bed containing at least one layerof adsorbent that can selectively adsorb at least one component in thefeed stream. In accordance with the methods of the present invention,the stages of the VPSA systems are provided with distinct cycles. Incertain embodiments, a temperature swing adsorption (TSA) system ispositioned upstream of the multiple stage VPSA systems for pretreatmentof the feed gases. In preferred embodiments of the invention, the firststage VPSA system provides regeneration gas for the TSA system, and/orthe VPSA second stage tail gas is recycled to the first stage VPSAsystem.

Exemplary low helium-containing feed gases suitable for treatment inaccordance with the present invention include, but are not limited tonatural gas streams and natural gas streams in which much or all of themethane has been removed. An exemplary low helium-containing feed gassuitable for treatment in accordance with the present invention cancontain helium and one or more of: nitrogen, carbon dioxide, methane,water, ethane, propane, i-butane, n-butane, i-pentane, n-pentane and/orhydrocarbons having equal to or greater than 6 carbon atoms (e.g.,hexane, benzene, toluene, xylene). Such feed gases may also includeother components such as: NO_(R), SO_(X), NH₃, H₂, H₂S and the like.

According to certain embodiments of the present invention, a temperatureswing adsorption (TSA) system for pretreatment of the feed gases can beincluded upstream of multiple stage PSA or VPSA systems. Depending onthe contaminants present in the helium-containing feed gas, the pressureswing adsorption processes could utilize super atmospheric operatingpressures only, i.e., as in PSA systems, or trans atmospheric operatingpressures (above and below ambient pressures), i.e., as in VPSA systems.If adsorbates (e.g., C₃ ⁺ hydrocarbons) are difficult to remove from theadsorbent(s) for example, it may be preferred or necessary to use VPSAsystem(s) rather than PSA system(s). In preferred embodiments of theinvention, the PSA or VPSA first stage provides regeneration gas for theTSA system, and/or at least a portion of the PSA or VPSA second stagetail gas is recycled to the PSA or VPSA first stage. It is expected thatmethods and systems in accordance with the present invention will beable to achieve about 10% higher helium recovery and about 24% morehelium throughput or productivity over some prior art systems.

In accordance with some embodiments of the invention, a temperatureswing adsorption (TSA) and two vacuum pressure swing adsorption (VPSA)systems are preferably employed when heavy contaminants such as heavyhydrocarbons (e.g., C₄ ⁺) and/or H₂S or the like are present in thehelium-containing feed gases. The TSA system can be used upstream of thetwo VPSA systems (configured as a two stage VPSA system) for heavycontaminant removal such as heavy hydrocarbons (e.g., C₄ ⁺, BTX (i.e.,benzene, toluene and/or xylene), H₂S, NO_(R), SO_(R), NH₃, H₂S and/orH₂0 and the like. Removal of such heavy contaminants by the TSA systemcan suppress degradation of the adsorbents in the downstream two stageVPSA or pressure swing adsorption (PSA) systems and processes. Morespecifically, the TSA is needed or desirable to suppress degradation ofthe stage one adsorbents due to irreversible adsorption using typicalVPSA desorption pressures if some heavy contaminants (e.g., BTX andheavy hydrocarbons) present in the helium-containing feed gas aretreated in the first stage VPSA system (i.e. some such adsorbents arenot easily desorbed using typical VPSA desorption pressures). Inaddition, if H₂ is present in the helium-containing feed gas, then ahydrogen removal unit (e.g., conventional deoxo unit) can be addedbetween the first and second stage VPSA systems (see for example, FIG.12).

In preferred embodiments of the invention, the tail gas or effluentleaving the feed end during bed regeneration of the first stage VPSAsystem is used as the purging gas for the upstream TSA process. Inaddition, the tail gas or effluent leaving the feed end during bedregeneration of the second stage VPSA system is recycled to the feedinlet of the first stage VPSA process to achieve improved heliumrecovery. As described hereinbelow, buffer tank(s) are preferably usedin some instances to smooth out flow, pressure and/or compositionfluctuations of the effluent stream(s) from one stage going into anotherstage(s) via the integration of the present invention.

The two stage PSA or VPSA cycles according to the present inventioninclude distinct cycles in stages one and two. The stage one PSA or VPSAcycle utilizes bottom-to-bottom equalization instead of a rinse stepthat is used in some prior art helium VPSA cycles and the stage twoPSA/VPSA cycle utilizes top-to-bottom equalization instead of a rinsestep that is used in some prior art helium VPSA cycles.

In addition, the present invention allows for full synchronization amongthe TSA and two stage VPSA systems to achieve continuous product andfeed steps in the helium recovery system. As mentioned above, the tailgas from the stage one VPSA system can be used as the regeneration orpurge gas for the upstream TSA system and a buffer tank can be used tosmooth out the stage one PSA or VPSA tail gas flows and/or compositionprior to sending the tail gas as the purging gas for the TSA systemduring bed regeneration. The TSA cycle time is preferably an integralmultiple (e.g., 15 times) of the stage one VPSA cycle time, and themultiplier depends on the impurities to be removed by the TSA system,and the duration of the TSA heating or cooling time required forspecified TSA bed sizes.

The present invention additionally is expected to allow for the tail gasfrom the stage two PSA or VPSA system to be recycled back to the feedend of the stage one PSA or VPSA system. The PSA or VPSA cycles for thetwo PSA or VPSA systems are synchronized so that the effluent from stageone goes to the stage two feed (typically via a buffer tank) without anyinterruption. Similarly, the effluent from the TSA system can be fedcontinuously (typically via a buffer tank) to the feed end of the firststage PSA system. In addition, all the purge gas for the TSA system ispreferably supplied from the tail gas from the stage one PSA system. Inaccordance with further aspects of the invention, the stage one PSA orVPSA system utilizes bottom-to-bottom bed equalization during theinitial re-pressurization of the stage one beds, thereby eliminating theneed for rinse steps used in some prior art systems that requirecompression to the first stage adsorption pressure and the stage two PSAor VPSA system utilizes top-to-bottom bed equalization during theinitial re-pressurization of the stage two beds, thereby eliminating theneed for rinse steps used in some prior art systems that requirecompression to the second stage adsorption pressure.

Depending on the type of feed gas and the system and process being used,the present invention can include some or all of the following features.Each bed in the stage one PSA or VPSA system can include three layers ofadsorbents, and each bed in stage two can preferably include a weakadsorbent (e.g., activated carbon or 5A zeolite) and a strong adsorbent(e.g., VSA-6 (such as VSA-6 8×12 zeolite from UOP, LLC of Des Plaines,Ill.) zeolite, LiX zeolite, CaX zeolite, or Z10-08 or Z10-08EP zeolites(both Z10-08 or Z10-08EP zeolites by Zeochem LLC) positioned on top ofthe weak adsorbent. The stage two VPSA system also preferably includesan adsorbent such as alumina positioned upstream of the weak adsorbent(which can provide for adsorption and/or flow distribution). This is incontrast to some prior art systems which have utilized activated carbonbeds in each bed of stages one and two of the VPSA systems for heliumrecovery. High performance and layered beds of adsorbents are used inthe TSA and VPSA systems of the present invention to achieve improvedhelium recoveries and throughputs. In addition, adsorbents selective forheavy contaminants present in the feed gas can be selected and arrangedin the TSA system to suppress degradation of the stage one PSA or VPSAsystem adsorbents. Each stage of the PSA or VPSA system preferablycontains four adsorbent beds utilizing different PSA or VPSA cycles withfull synchronization between the stages to handle various streams tocontinuously deliver high purity helium product. In the aforementionedembodiments having layered beds of selected adsorbents in the two stageVPSA systems, it is expected that modest adsorption (e.g., about 4.8bars) and desorption (e.g., about 0.6096 bars) pressures can be usedsuch that capital and operating costs of the helium recovery system canthereby be reduced.

In accordance with the present invention, improved adsorberconfigurations and cycles are therefore disclosed for use in multiple(e.g., two) stage PSA or VPSA systems for recovering helium from lowhelium-containing feed gases. In addition, a temperature swingadsorption (TSA) system can be utilized upstream of the two stage PSA orVPSA systems to remove heavy contaminants such as H₂S, hydrocarbons(e.g., C₄ ⁺) and the like. As mentioned hereinabove and as discussedbelow, the waste gas (or stage one VPSA tail gas) from the stage oneVPSA system is preferably used as the regeneration gas for the upstreamTSA system, and the waste gas (or stage two VPSA tail gas) from thestage two VPSA system is preferably recycled back to the first stagefeed. As also discussed herein, the present invention is expected toprovide for the use of improved layered bed configurations of thevarious adsorbents to achieve improved helium recovery at reducedcapital and operating costs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of a helium recovery system using a temperatureswing adsorption (TSA) system upstream of two vacuum pressure swingadsorption (VPSA) systems in accordance with one embodiment of thepresent invention.

FIG. 2 shows an exemplary TSA bed configuration for use in accordancewith the present invention.

FIG. 3 illustrates a three bed TSA system used for heavy components(e.g., C₆ ⁺ hydrocarbons, H₂S) removal from various feed gases inaccordance with the present invention.

FIG. 4 shows a TSA cycle for the TSA system of FIG. 3.

FIG. 5 illustrates a two stage PSA bed arrangement depicting layers ofadsorbents used in first and second stage PSA systems.

FIG. 6 shows a four adsorbent bed configuration for a stage one VPSAsystem and process in accordance with the present invention.

FIG. 7 shows a stage one VPSA cycle for the VPSA system of FIG. 6.

FIG. 8 shows a four adsorbent bed configuration for a stage two VPSAsystem in accordance with the present invention.

FIG. 9 shows a stage two VPSA cycle for the VPSA system of FIG. 8.

FIG. 10 shows a computer-simulated comparison of the two stage heliumrecovery process of the present invention using layered beds ofadsorbents and improved VPSA cycles versus the prior art helium recoverycycles disclosed in U.S. Pat. No. 5,542,966 by D'Amico et al.

FIG. 11 shows an alternative embodiment of the present invention using astage two VPSA system without the upstream TSA system shown in FIG. 1.

FIG. 12 shows another alternative embodiment of the present inventionusing a modified version of FIG. 11 for the case where the feed gascontains H₂.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides method and systems for recovering heliumfrom low helium-containing feed gases. As already mentioned, lowhelium-containing gases contain less than about 10 volume % helium, andmore typically, less than about 5% helium by volume. In accordance withsome embodiments of the invention, two stages of PSA or VPSA systems,with each system having a distinct cycle, are provided. Such embodimentscould include two PSA systems, two VPSA systems or a combination of aPSA or VPSA system. In addition, it is expected that more than twostages of PSA and/or VPSA systems could be implemented according to theinvention. In alternative embodiments of the invention, any of theembodiments of the multiple (e.g., two) stage PSA or VPSA systems caninclude a TSA system upstream of the first stage for pretreatment of thefeed gases. In preferred embodiments of the invention, the PSA or VPSAfirst stage system provides regeneration gas for the TSA system, and/orthe PSA or VPSA second stage tail gas is recycled to the first stageVPSA system.

Each stage of the PSA or VPSA systems contain multiple (e.g. four) beds,each bed containing one or more layers of adsorbents. The adsorbents arechosen to selectively adsorb at least one component in the feed stream.Adsorbents can further be selected to be placed within the TSA or one ofthe stages of the PSA or VPSA systems depending on the type of adsorbateto be removed. For example and depending on the type of feed gas andcontaminants to be removed therefrom, the TSA can be used to removecontaminants that would degrade the adsorbents in the downstream PSA orVPSA system(s).

Depending on the type of feed gas and the system and process being used,the present invention can include some or all of the following features.Each bed in the stage one PSA or VPSA system can include three layers ofadsorbents, and each bed in stage two can preferably include a weakadsorbent (e.g., activated carbon or 5A zeolite) and a strong adsorbent(e.g., VSA-6 zeolite, LiX zeolite, CaX zeolite, or Z10-08 or Z10-08EPzeolites (both Z10-08 or Z10-08EP zeolites by Zeochem LLC) positioned ontop of the weak adsorbent. Stage two also preferably includes anadsorbent such as alumina positioned upstream of the weak adsorbent(which can provide for adsorption and/or flow distribution). Suchadsorbent configurations are in contrast to some prior art systems whichhave utilized activated carbon beds in each bed of stages one and two ofthe VPSA systems for helium recovery. High performance and layered bedsof adsorbents are used in the TSA and VPSA systems of the presentinvention to achieve improved helium recoveries and throughputs. Inaddition, adsorbents selective for heavy contaminants present in thefeed gas can be selected and arranged in the TSA system to suppressdegradation of the stage one PSA or VPSA system adsorbents. Each stageof the PSA or VPSA system preferably contains four adsorbent bedsutilizing different PSA or VPSA cycles with full synchronization betweenthe stages to handle various streams to continuously deliver high purityhelium product. In the aforementioned embodiments having layered beds ofselected adsorbents in the two stage VPSA systems, it is expected thatmodest adsorption (e.g., about 4.8 bars) and desorption (e.g., about0.6096 bars) pressures can be used such that capital and operating costsof the helium recovery system can thereby be reduced.

The helium-containing feed gas typically contains large concentrationsof N₂ and trace quantities of hydrocarbons, making prior art systemsthat use carbon beds for heavy contaminant removal inefficient,uneconomical or unsustainable as the presence of some heavy hydrocarbonsor other heavy contaminants can degrade the carbon adsorbents. Use of aTSA system upstream of the multiple stage PSA or VPSA systems cantherefore allow for removal of such contaminants and regeneration of theselected adsorbents.

The systems of the present invention are expected to provide a smallersystem footprint, lower capital cost and lower operating cost than priorart systems. In some cases, it is expected that about 24% morethroughput and about 10% higher helium recovery could be achieved usingthe helium recovery systems of the present invention.

Various adsorbents could be utilized in accordance with the TSA and PSAor VPSA systems of the present invention. The adsorbents are selected toremove various heavy contaminants and impurities and/or other componentspresent in the low helium-containing feed gas. For example and while notto be construed as limiting, aluminosilicates such as HiSiv adsorbent(e.g. HiSiv-3000) (from UOP, LLP of Des Plaines, Ill., referred to as“UOP”) or ZSM 5 supported on gamma alumina, titanium silicates such asETS-10 (from Engelhard, which is now BASF Catalysts, LLC) and activatedcarbons such as BAX-1100 (from Westvaco, Corporation) and combinationsthereof could be used for C₆ ⁺ hydrocarbons removal in the adsorberbeds. Clinoptilolite (e.g., barium ion exchanged clinoptilolite) (fromUOP, LLP of Des Plaines, Ill.) is also expected to be suitable for usein accordance with the present invention for some feed streams (forexample, for H₂S removal). In addition, alumina may also be used forcontaminant removal (including water) and/or to provide for flowdistribution. Selection of such adsorbents, combinations of suchadsorbents and the layering or configurations within the beds of theadsorbers can vary depending on the impurities or heavy contaminants tobe removed from the feed gas, the concentrations of such impurities orheavy contaminants and the like.

It should be noted, however, that activated carbon adsorbents are notlikely to be preferred for use in the TSA systems where the temperatureswings between adsorption and desorption steps are high enough to causeunacceptable or undesirable carbon adsorbent degradation.Aluminosilicates such as HiSiv adsorbents, ZSM 5 supported on gammaalumina, titanium silicates such as ETS-10, clinoptilolite (e.g., bariumion exchanged clinoptilolite) and/or alumina adsorbents are thereforelikely to be preferred in the TSA systems and processes over theactivated carbons because of their better thermal and hydrothermalstability.

In addition, activated or treated activated carbon such as Centaur®carbon from (from Calgon Corporation) or Selexorb® COS (from BASF) maybe suitable for SOx, NOx and/or H₂S removal. In addition, silica gelcould be used for removing C₂-C₅ impurities. Depending on the feed gascomposition and the concentration of the impurities, the removal ofC₂-C₅ adsorbents could be accomplished in the TSA system and/or the PSAor VPSA stage one systems. While not to be construed as limiting, SOxand NOx are likely to be removed in the TSA system.

Activated carbon adsorbents can be used for example in the PSA or VPSAsystems for CH₄ and CO₂ removal. The PSA or VPSA systems could alsoinclude alumina upstream of such adsorbents for water removal. Zeolitessuch as 5A, Li—X, or H-15 (from UOP) can be used to remove componentssuch as N₂ and CO (and any oxygen and/or argon present in thehelium-containing stream) to produce high purity (preferably >99.9% fromthe second stage PSA or VPSA). First stage effluent in accordance withthe present invention is expected to be about 70-90% helium by volume.

In accordance with the present invention, adsorbents can therefore beselected for use in the TSA system for heavy contaminant removal. Inaddition, adsorbents can be selected for use in the multiple stage PSAor VPSA systems for removal of adsorbates such as N₂, CH₄, CO₂, O₂, Ar,residual H₂O and residual hydrodcarbons.

Referring now to FIG. 1, a schematic of a helium recovery system andprocess using a temperature swing adsorption (TSA) system upstream oftwo vacuum pressure swing adsorption (VPSA) systems is illustrated. Thesystem shown in FIG. 1 includes TSA system 12 and VPSA stage one system24 coupled to VPSA stage two system 38. As described herein, TSA system12 receives feed gas 14 and produces TSA waste 16 and ahelium-containing pretreated feed gas effluent 18. Effluent 18 is fed tobuffer tank 20 such that feed gas 22 can be provided to VPSA stage onesystem 24. Waste 16 from the TSA system is sent to the flare stack orscrubbers or exhaust vent.

VPSA stage one system 24 produces helium-containing purified feed gaseffluent gas 32, which is provided to buffer tank 34 and tail gas 26.Tank 34 is used to smooth transients and provide feed gas 36 to VPSAstage two system 38. As can be seen from FIG. 1, at least a portion 26 aof the waste gas 26 from the VPSA stage one process can be used as theregeneration gas 30 for the upstream TSA system 12. Buffer tank 28 isprovided to smooth transients in the system. The remainder 26 b of tailgas 26 can be discarded as waste gas.

VPSA stage two system 38 produces a high purity helium gas 40. Asfurther shown in FIG. 1, waste (or tail gas) 42 can be compressed inrecycle compressor 44 and returned to VPSA stage one as stream 46.Stream 46 can be combined with effluent 18 and used as feed gas 22.

If hydrogen is present in the feed gas, a deoxo unit and water removalunit such as shown in FIG. 12 can also be included (for example, betweenstage one VPSA system 24 and stage two VPSA system 38).

FIG. 2 shows the details for one adsorber bed 50 in an exemplary TSAprocess in accordance with the present invention. In a preferred mode ofoperation, the TSA system is used for the removal of the heavyimpurities such as BTX (benzene, toluene and/or xylene), H₂O, H₂S, NH₃and HCl and heavier hydrocarbons C₅ ⁺ contained in various feed gases.In some instances, however, where the feed gas contains C₂-C₅hydrocarbons but does not contain C₆ ⁺ hydrocarbons, the C₂-C₅hydrocarbons can be removed by silica gel adsorbent upstream ofactivated carbon adsorbent in the PSA or VPSA system. In this instance,the silica gel suppresses degradation of the carbon adsorbent due toirreversible adsorption of the C₄ hydrocarbons. Referring to FIG. 2, S1adsorbent (e.g., HiSiv 3000, alumina, ETS-10) and S2 adsorbent (e.g.,barium ion exchanged clinoptilolite) can be used in each bed of thethree beds of the TSA system. Alternatively and depending on the feedgas composition and concentrations of impurities, S1 could for examplebe a layer of alumina and S2 could for example be a layer ofclinoptilolite (e.g., preferably barium ion exchanged clinoptilolite).

As can be seen from FIG. 2, feed gas 14 is preferably fed to the top ofthe adsorber and effluent 18 is removed from the bottom of the adsorberwhile waste gas 16 is removed from the top of the adsorber. Regenerationgas(es) 30/48 flows through the adsorbers to perform the associatedheating and cooling steps as disclosed in Table 1. It will beappreciated that the flow directions could be reversed.

FIG. 3 illustrates a three bed temperature swing adsorption (TSA) systemand process suitable for removal of heavy contaminants (e.g., C₆ ⁺hydrocarbons, H₂S) from various helium-containing feed gases inaccordance with the invention. The TSA system can also be referred to asa pretreatment system for the downstream two stage VPSA systems.Referring to FIG. 3, the pretreatment beds 50 a, 50 b and 50 c arearranged in parallel, so that when one pretreatment bed is online toremove heavy impurities (e.g., C₆ ⁺ hydrocarbons and H₂S) from the feedgas, the other beds are undergoing the regeneration steps (heating andcooling).

As can be seen from FIG. 3, the three bed TSA pretreatment systemincludes three-adsorber beds, ON/OFF valves and associated piping andfittings. The valve switching logic for the pretreatment three bed TSAprocess is shown below in Table 1. Referring to Table 1 and FIG. 3, oneembodiment of the pretreatment system (or TSA process) in accordancewith the present invention is provided over one complete TSA cycle.

TABLE 1 Valve Firing Sequence for Three Bed TSA Pretreatment System ofFIG. 3. Step 1 2 3 PB1 Online Heating Cooling PB2 Cooling Online HeatingPB3 Heating Cooling Online Valve No. V1 O C C V2 C O C V3 C C O V4 C C OV5 O C C V6 C O C V7 C C O V8 O C C V9 C O C V10 C O C V11 C C O V12 O CC V13 O C C V14 C O C V15 C C O V16 C O C V17 C C O V18 O C C V19 O O OV20 C C C Online: Adsorption step for heavy components removal. Heatingis counter-current with respect to feed direction. Cooling is co-currentwith respect to feed direction. C = valve in closed position =valve inopened position

Step No. 1

In step 1, the first pretreatment bed 50 a (PB1) is receiving compressedfeed gas 14 via feed compressor 52. During this step, valves 1 and 13(V1 and V13) are in the open positions. The compressed feed gas flowsthrough the first pretreatment bed 50 a (PB1) to remove heavycomponents. Thus, the first pretreatment bed 50 a is online, and heavycomponents such as H₂O and H₂S are removed by S1 adsorbent (e.g.,alumina) and S2 adsorbent (e.g., HiSiv 3000, ETS, or clinoptilolite,such as barium ion exchanged clinoptilolite). S1 and S2 can varydepending on the feed gas composition and impurity concentrationstherein. During the time bed 50 a (PB1) is online, the secondpretreatment bed 50 b (PB2) is in the cooling step (valves V5 and V8 areopened), and the third pretreatment bed 50 c (PB3) is in the heatingstep (valves V12, V18, and V19 are opened). The effluent obtained duringthe co-current cooling step (co-current with respect to feed step) ofthe second pretreatment bed 50 b (PB2) is heated by the processregenerator heater 54 prior to passing to the third pretreatment bed 50c (PB3) that is undergoing the countercurrent (with respect to feed)heating step. The purging gas 48 for bed regeneration can be obtainedfrom an external source (e.g., nitrogen) or the stage one VPSA tail gas.In the preferred mode of operation, the regeneration gas is preferablyfrom the VPSA stage one recycle tail gas 30. If there is insufficienttail gas 30, then external gas 48 can be added as additionalregeneration gas for the TSA system. The effluent 18 from the firstpretreatment bed 50 a (PB1), is passed to the PSA or VPSA process, viavalve 13 (V13).

Step No. 2

In step 2, the second pretreatment bed 50 b (PB2) is receivingcompressed feed gas 14, via feed compressor 52. During this step, valves2 and 14 (V2 and V14) are in the open positions. The compressed feed gasflows through the second pretreatment bed 50 b (PB2) to remove heavycomponents. Thus, the second pretreatment bed 50 b is online, and heavycomponents such as H₂O and H₂S are removed by S1 adsorbent (e.g.,alumina) and S2 adsorbent (e.g., e.g., HiSiv 3000, ETS, orclinoptilolite, such as barium ion exchanged clinoptilolite). During thetime bed 50 b (PB2) is online, the third pretreatment bed 50 c (PB3) isin the cooling step (valves V6 and V9 opened), and the firstpretreatment bed 50 a (PB1) is in the heating step (valves V10, V16, andV19 opened). The effluent obtained during the co-current cooling step(co-current with respect to feed step) of the third pretreatment bed 50c (PB3) is heated by the process regenerator heater 54 prior to passingto the first pretreatment bed 50 a (PB1) that is undergoing thecountercurrent (with respect to feed) heating step. The purging gas 48for bed regeneration can be obtained from an external source (e.g.,nitrogen) or the stage one VPSA tail gas. In the preferred mode ofoperation, the regeneration gas is preferably from the VPSA stage onerecycle tail gas 30. If there is insufficient tail gas 30, then externalgas 48 can be added as additional regeneration gas for the TSA system.The effluent 18 from the second pretreatment bed 50 b (PB2), is passedto the PSA or VPSA process, via valve 14 (V14).

Step No. 3

In step 3, the third pretreatment bed 50 c (PB3) is receiving compressedfeed gas 14, via feed compressor 52. During this step, valves 3 and 15(V3 and V15) are in the open positions. The compressed feed gas flowsthrough the third pretreatment bed 50 c (PB3) to remove heavycomponents. Thus, the third pretreatment bed is online, and heavycomponents such as H₂O and H₂₅ are removed by S1 adsorbent (e.g.,alumina) and S2 adsorbent (e.g., HiSiv 3000, ETS, or clinoptilolite,such as barium ion exchanged clinoptilolite). During the time bed 50 c(PB3) is online, the first pretreatment bed 50 a (PB1) is in the coolingstep (valves V4 and V7 are opened), and the second pretreatment bed 50 b(PB2) is in the heating step (valves V11, V17, and V19 are opened). Theeffluent obtained during the co-current cooling step (co-current withrespect to feed step) of the first pretreatment bed 50 a (PB 1) isheated by the process regenerator heater 54 prior to passing to thesecond pretreatment bed 50 b (PB2) that is undergoing the countercurrent(with respect to feed) heating step. The purging gas 48 for bedregeneration can be obtained from an external source (e.g., nitrogen) orthe stage one VPSA tail gas. In the preferred mode of operation, theregeneration gas is preferably from the VPSA stage one recycle tail gas30. If there is insufficient tail gas 30, then external gas 48 can beadded as additional regeneration gas for the TSA system. The effluent 18from the third pretreatment bed 50 c (PB3) is passed to the PSA or VPSAstage one system.

FIG. 4 shows the TSA cycle for the TSA system of FIG. 3. It can be notedfrom FIGS. 3 and 4 and from Table 1 that the three beds operate inparallel, and during ⅓ of the total cycle time, one of the beds is inthe adsorption step (online), while the other beds are undergoing theheating/cooling steps. Thus, the pretreatment system of FIG. 3, usingthe valve logic in Table 1, delivers a continuous feed stream 18 to thedownstream PSA or VPSA stage one process and system. As noted above, inthe preferred mode of operation, the feed flow is downward into the TSAadsorber beds, and the S1 and S2 adsorbents are placed in TSA beds forheavy contaminant removal while the other adsorbents (e.g., silica gel,activated carbons and zeolites) are contained in VPSA beds positioneddownstream of the TSA beds.

Referring now to FIG. 5, a two stage PSA bed arrangement depictinglayers of adsorbents used in first and second stage PSA systems isshown. More specifically, FIG. 5 shows the layered bed design for use instages one and two adsorbers in accordance with an embodiment of thepresent invention. Depending on the feed gas, three layers of adsorbentsmay preferably be used in each of the VPSA process. As mentioned above,the sources of low helium-containing gas can come from natural gas wellsor natural gas streams in which the methane has been removed (orsubstantially removed). For simplicity and clarity and for purposes ofillustration in disclosing the features of the present invention, a feedgas containing the following composition by volume % is considered:4.25% He, 83.478% N₂, 7.661% CO₂, 0.4% O₂, 0.6% H₂O, 2.762% CH₄, 0.265%ethane, 0.25% propane, 0.056% i-butane, 0.103% n-butane, 0.043%i-pentane, 0.041% n-pentane and 0.091% C₆ ⁺. Thus for example, using theaforementioned feed composition, the feed gas can be passed through theTSA system (see FIG. 3) to remove the heavy contaminants such asi-pentane, n-pentane and C₆ ⁺ prior to passing to the downstream twostage VPSA systems. Each stage of downstream VPSA system preferablycontains four adsorbent beds.

FIG. 6 shows four adsorbent beds 56 a-56 d (B1, B2, B3 and B4) andassociated valves and conduits of the VPSA stage one system and process.In FIG. 6, the first stage (stage 1) VPSA system has three layers ofadsorbents in each bed, for example alumina in layer 1, activated carbonin layer 2, and zeolite in layer 3. In some modes of operation, VPSAstage one beds therefore include alumina at the feed end followed byactivated carbon for the removal of CO₂ and CH₄, and then zeolite forthe removal of bulk N₂. If C₂-C₅ hydrocarbons are present in the stageone feed gas composition, a layer of silica gel is preferably includedbetween the alumina and carbon layers for removal of the C₂-C₅hydrocarbons. FIG. 7 shows the VPSA stage one cycle for the VPSA systemof FIG. 6. Referring to FIGS. 1, 5, 6 and 7, a VPSA stage one processused in helium recovery in accordance with the invention is providedover one complete VPSA cycle, and the VPSA valve switching and steps aregiven in Tables 2 and 3, respectively.

Stage 1 VPSA Process Steps (FIGS. 6 and 7)

Step 1 (AD1): Bed 56 a (B1) is in the first adsorption step (AD1) atabout 4.8 bars, while bed 56 b (B2) is undergoing countercurrentblowdown (BD), bed 56 c (B3) is undergoing the first equalizationfalling step (EQ1DN), and bed 56 d (B4) is undergoing the secondpressure equalization rising step (EQ2UP).

Step 2 (AD2/PP1): Bed 56 a (B1) is in the second adsorption step (AD2)and is also supplying product gas to bed 56 d (B4) that is undergoingthe first product pressurization (PP1) step. During the same time, beds56 b (B2), 56 c (B3) and 56 d (B4) are undergoing purge, cocurrentdepressurization and first product pressurization, respectively.

Step 3 (AD3/PP2): Bed 56 a (B1) is in the third adsorption step (AD3),and is also supplying product gas to bed 56 d (B4) that is undergoingthe second product pressurization (PP2) step. During the same timeperiod, beds 56 b (B2), 56 c (B3) and 56 d (B4) are undergoing the firstequalization rising step at the feed end (bottom EQ1UP), secondequalization falling (bottom EQ2DN) step at the feed end, and secondproduct pressurization step (PP2), respectively.

Step 4 (EQ1DN or top-to-top bed equalization): Bed 56 a (B1) isundergoing the first equalization falling step (EQ1DN), while bed 56 b(B2) receives the gas from bed 56 a (B1) and is undergoing the secondequalization rising step (EQ2UP). Beds 56 c (B3) and 56 d (B4) are nowundergoing blowdown (BD) and the first adsorption step (AD1),respectively.

Step 5 (PPG): Bed 56 a (B1) is undergoing cocurrent depressurizationstep to provide purge gas (PPG) to bed 56 c (B3), while beds 56 b (B2)and 56 d (B4) are undergoing first product pressurization (PP1) and thesecond adsorption step (AD2), respectively.

Step 6 (EQ2DN or bottom-to-bottom bed equalization): Bed 56 a (B1)undergoes a second equalization falling step at the feed end (EQ2DN) bysending low pressure equalization gas (feed end) to bed 56 c (B3) thatis undergoing the first equalization rising (EQ1UP) step. Beds 56 b (B2)and 56 d (B4) are undergoing the second product pressurization (PP2) andthird adsorption step (AD3), respectively.

Step 7 (BD): Beds 56 a (B1) and 56 b (B2) undergo the countercurrentblowdown (BD) and first adsorption (AD1) step, respectively. During thistime beds 56 c (B3) and 56 d (B4) are undergoing bed-to-bedequalization, i.e., beds 56 c (B3) and 56 d (B4) are undergoing thesecond equalization rising (Eq2UP) and first equalization falling(EQ1DN) steps, respectively.

Step 8 (PG): Bed 56 a (B1) is now receiving purge gas (PG) from bed 56 d(B4), and beds 56 b (B2) and 56 c (B3) are undergoing the secondadsorption step (AD2) and first product pressurization (PP1) step,respectively.

Step 9 (EQ1UP or bottom-to-bottom bed equalization): Bed 56 a (B1) isundergoing the first equalization rising step (EQ1UP) by receiving lowpressure equalization gas (feed end) from bed 56 d (B4) that isundergoing the second equalization falling step (EQ2DN) at the feed end.During the same time, beds 56 b (B2) and 56 c (B3) are undergoing thethird adsorption step (AD3) and the second product pressurization (PP2),respectively.

Step 10 (EQ2UP or top-to-top bed equalization): Bed 56 a (B1) isundergoing the second equalization rising step (EQ2UP) by receiving highpressure equalization gas from bed 56 b (B2) that is undergoing thefirst equalization falling step (EQ1DN). During the same time, beds 56 c(B3) and 56 d (B4) are undergoing the first adsorption (AD1) step andcountercurrent blowdown step, respectively.

Step 11 (PP1): Bed 56 a (B1) is receiving first product pressurization(PP1) gas from bed 56 c (B3) that is also in the second adsorption step(AD2), while bed 56 b (B2) is undergoing cocurrent depressurization stepto provide purge gas (PPG) to bed 56 d (B4).

Step 12 (PP2): Bed 56 a (B1) is receiving second product pressurization(PP2) gas from bed 56 c (B3) that is also in the third adsorption step(AD3). During the same time, bed 56 b (B2) undergoes a secondequalization falling step (EQ2DN) at the feed end, by sending lowpressure equalization gas to bed 56 d (B4) (feed end) that is undergoingthe first equalization rising (EQ1UP) step.

During the adsorption (AD) steps, product that is not supply product gasto another bed undergoing product pressurization is being supplied tobuffer tank 34 and subsequently as stage two VPSA system feed 36. Thecontrol valve shown in FIG. 6 can be used to control or moderate theflow going to stage 2. In addition, the tail gas 26 from the four bedscan be sent to the flare stack or scrubbers or exhaust vent and/orrecycled to the TSA system as discussed above via vacuum pump (VP) 60.PV-1 and PV-2 are process control valves that can control or modulatethe flow of gas going in and out of the beds.

A summary of the aforementioned twelve steps are given in Tables 2 and3. In particular, Table 2 summarizes the valve sequence over onecomplete cycle for the four bed PSA process shown in FIGS. 6 and 7, andTable 3 gives the respective time intervals and the corresponding statusof each bed during one complete PSA cycle. It can be seen from Tables 2and 3 that the four beds operate in parallel, and during ¼ of the totalcycle time one of the beds is in the adsorption step, while the otherbeds are each undergoing one of the other steps as disclosed in the VPSAcycle.

Table 4 gives an example of the operating conditions and the VPSAprocess performance using three layers of adsorbents (alumina, silicagel or activated carbon, and zeolite), in each adsorber of the four bedVPSA system and process shown in FIG. 6. In this example, the firstlayer (layer 1 in FIG. 6) is 1.0 ft of alumina, followed by 5.0 ft ofactivated carbon (layer 2 in FIG. 6), then 5.0 ft of UOP VSA-6 zeolite(layer 3 in FIG. 6). In the table, the symbols have the followingmeaning. kPa=1000 Pa=S.I. unit for pressure (1.0 atm.=101.323 kPa),s=time unit in seconds. In addition, the VPSA stage one waste gas (ortail gas), obtained during the regeneration steps of the VPSA stage onecycle (FIG. 7), is used as regeneration gas for the upstream TSA processin FIG. 3.

TABLE 2 Stage 1 Four Bed VPSA Valve Switching (O = OPENED, C = CLOSED)Step 1 2 3 4 5 6 7 8 9 10 11 12 Bed 1 AD1 AD2/ AD3/ EQ1DN PPG EQ2DN BDPG EQ1UP EQ2UP PP1 PP2 (BD1) PP1 PP2 Bed 2 BD PG EQ1UP EQ2UP PP1 PP2 AD1AD2/ AD3/ EQ1DN PPG EQ2DN (BD2) PP1 PP2 Bed 3 EQ1DN PPG EQ2DN BD PGEQ1UP EQ2UP PP1 PP2 AD1 AD2/ AD3/ (BD3) PP1 PP2 Bed 4 EQ2UP PP1 PP2 AD1AD2/ AD3/ EQ1DN PPG EQ2DN BD PG EQ1UP (BD4) PP1 PP2 Valve No. V31 O O OC C C C C C C C C V32 C C C C C C O O O C C C V33 C C C C C C C C C O OO V34 C C C O O O C C C C C C V35 O O C O O C O O C O O C V36 C C C C CC O O C C C C V37 O O C C C C C C C C C C V38 C C C O O C C C C C C CV39 C C C C C C C C C O O C V40 C O O C O O C O O C O O V41 O O O C C CC C C C C C V42 C C C C C C O O O C C C V43 C C C C C C C C C O O O V44C C C O O O C C C C C C V45 C C C C O C C O C C C C V46 C O C C C C C CC C O C V47 C O C C O C C C C C C C V48 C C C C C C C O C C O C V49 C CC O C C C C C O O O V50 C C C O O O C C C O C C V51 O C C C C C O O O CC C V52 O O O C C C O C C C C C V53 C C C C C O C C O C C C V54 C C O CC C C C C C C O V55 C C O C C O C C C C C C V56 C C C C C C C C O C C OV57 O O O O O O O O O O O O V58 C C C C C C C C C C C C

TABLE 3 Time Interval and Step Sequence of Stage 1 VPSA Cycle (FIG. 7)Step Time Number Interval BED #1 BED #2 BED #3 BED #4 1  0-25 AD1 BDEQ1DN EQ2UP 2 25-45 AD2/PP1 PG PPG PP1 3 45-60 AD3/PP2 EQ1UP EQ2DN PP2 460-85 EQ1DN EQ2UP BD AD1 5  85-105 PPG PP1 PG AD2/PP1 6 105-120 EQ2DNPP2 EQ1UP AD3/PP2 7 120-145 BD AD1 EQ2UP EQ1DN 8 145-165 PG AD2/PP1 PP1PPG 9 165-180 EQ1UP AD3/PP2 PP2 EQ2DN 10 180-205 EQ2UP EQ1DN AD1 BD 11205-225 PP1 PPG AD2/PP1 PG 12 225-240 PP2 EQ2DN AD3/PP2 EQ1UP AD1 =First Adsorption Step AD2/PP1 = Second Adsorption Step/First productpressurization AD3/PP2 = Third Adsorption Step/Second productpressurization EQ1DN = First Equalization Down or top-to-top bedequalization PPG = Provide Purge Gas EQ2DN = Second Equalization Down orbottom-to-bottom bed equalization BD = Blowdown PG = Purge EQ1UP = FirstEqualization Up or bottom-to-bottom bed equalization EQ2UP = SecondEqualization Up or top-to-top bed equalization PP1 = First ProductPressurization PP2 = Second Product Pressurization

Table 4 (Stage 1 Four Bed VPSA Process Details):

An example of the operating conditions and the VPSA process performanceusing 1.0 ft alumina (layer 1), 5.0 ft activated carbon (layer 2), and 5ft of VSA6 zeolite (layer 3) in a layered bed arrangement in the fourbed VPSA process of FIGS. 6 and 7 (bed diameter=9.0 ft) is provided. Theresults shown below were obtained from computer simulation using a feedmixture of 4.25% He, 83.48% N₂, 11.27% CO₂, 0.4% O₂, 0.6% H₂O. (UpstreamTSA process removes ethane, propane, i-butane, n-butane, i-pentane,n-pentane and C₆ ⁺ and the like):

Cycle time (s) 240 Adsorbent in first layer of Bed alumina Amount ofalumina (lb/bed): 3,054 Adsorbent in second layer of bed: activatedcarbon Amount of activated carbon (lb/bed): 9,976 Adsorbent in thirdlayer of bed: VSA-6 Amount of VSA-6 zeolite (lb/bed): 13,147 HighPressure: 480 kPa Low Pressure: 60.96 kPa Feed Flowrate: 3022.36 scfmHelium Purity: 90% (Feed to Stage 2 VPSA) PSA Per Pass Helium Recovery:65% Stage 1 Tail Gas (for TSA Regen.) ~86% N₂, 2.3% He, 11.4% CO₂Temperature: 308 K

FIG. 8 shows four adsorbent beds 58 a-58 d (B1, B2, B3 and B4) andassociated valves and conduits for a VPSA stage two system and processin accordance with the present invention. In FIG. 8, the VPSA secondstage (Stage 2) system has three layers of adsorbents, for example layer1 in stage two contains at the feed end alumina balls for flowdistribution followed by activated carbon, then a strong zeolite towardsthe product end of the second stage beds. FIG. 9 shows the VPSA stagetwo cycle for the VPSA system of FIG. 8. Referring to FIGS. 1, 5, 8 and9, the VPSA stage two process used in helium recovery is provided overone complete VPSA cycle, and the VPSA valve switching and steps aregiven in Tables 5 and 6, respectively.

Stage 2 VPSA Process (FIGS. 8 and 9):

Step 1 (AD1): Bed 58 a (B5) is in the first adsorption step (AD1) atabout 4.8 bars, while bed 58 b (B6) is undergoing countercurrentblowdown (BD), bed 58 c (B7) is undergoing the first equalizationfalling step (EQ1DN), and bed 58 d (B8) is undergoing the secondpressure equalization rising step (EQ2UP).

Step 2 (AD2/PP1): Bed 58 a (B5) is in the second adsorption step (AD2)and is also supplying product gas to bed 58 d (B8) that is undergoingthe first product pressurization (PP1) step. During the same time, beds58 b (B6), 58 c (B7) and 58 d (B8) are undergoing purge, cocurrentdepressurization and first product pressurization, respectively.

Step 3 (AD3/PP2): Bed 58 a (B5) is in the third adsorption step (AD3),and is also supplying product gas to bed 58 d (B8) that is undergoingthe second product pressurization (PP2) step. During the same timeperiod, beds 58 b (B6), 58 c (B7) and 58 d (B8) are undergoing the firstequalization rising step at the feed end (bottom EQ1UP), secondequalization falling (bottom EQ2DN) step at the product end, and secondproduct pressurization step (PP2), respectively.

Step 4 (EQ1DN or top-to-top bed equalization): Bed 58 a (B5) isundergoing the first equalization falling step (EQ1DN), while bed 58 b(B6) receives the gas from bed 58 a (B5) and is undergoing the secondequalization rising step (EQ2UP). Beds 58 c (B7) and 58 d (B8) are nowundergoing blowdown (BD) and the first adsorption step (AD1),respectively.

Step 5 (PPG): Bed 58 a (B5) is undergoing cocurrent depressurizationstep to provide purge gas (PPG) to bed 58 c (B7), while beds 58 b (B6)and 58 d (B8) are undergoing first product pressurization (PP1) and thesecond adsorption step (AD2), respectively.

Step 6 (EQ2DN or top-to-bottom bed equalization): Bed 58 a (B5)undergoes a second equalization falling step at the product end (EQ2DN)by sending low pressure equalization gas to bed 58 c (B7) that isundergoing the first equalization rising (EQ1UP) step at the feed end.Beds 58 b (B6) and 58 d (B8) are undergoing the second productpressurization (PP2) and third adsorption step (AD3), respectively.

Step 7 (BD): Beds 58 a (B5) and 58 b (B6) undergo the countercurrentblowdown (BD) and first adsorption (AD1) step, respectively. During thistime, beds 58 c (B7) and 58 d (B8) are undergoing bed-to-bedequalization, i.e., beds 7 and 8 are undergoing the second equalizationrising (Eq2UP) and first equalization falling (EQ1DN) steps,respectively.

Step 8 (PG): Bed 58 a (B5) is now receiving purge gas (PG) from bed 58 d(B8), and beds 58 b (B6) and 58 c (B7) are undergoing the secondadsorption step (AD2) and first product pressurization (PP1) step,respectively.

Step 9 (EQ1UP or top-to-bottom bed equalization): Bed 58 a (B5) isundergoing the first equalization rising step (EQ1UP) by receiving lowpressure equalization gas (feed end) from bed 58 d (B8) that isundergoing the second equalization falling step (EQ2DN) at the productend. During the same time, beds 58 b (B6) and 58 c (B7) are undergoingthe third adsorption step (AD3) and the second product pressurization(PP2), respectively.

Step 10 (EQ2UP or top-to-top bed equalization): Bed 58 a (B5) isundergoing the second equalization rising step (EQ2UP) by receiving highpressure equalization gas from bed 58 b (B6) that is undergoing thefirst equalization falling step (EQ1DN). During the same time, beds 58 c(B7) and 58 d (B8) are undergoing the first adsorption (AD1) step andcountercurrent blowdown step, respectively.

Step 11 (PP1) Bed 58 a (B5) is receiving first product pressurization(PP1) gas from bed 58 c (B7) that is also in the second adsorption step(AD2), while bed 58 b (B6) is undergoing cocurrent depressurization stepto provide purge gas (PPG) to bed 58 d (B8).

Step 12 (PP2) Bed 58 a (B5) is receiving second product pressurization(PP2) gas from bed 58 c (B7) that is also in the third adsorption step(AD3). During the same time, bed 58 b (B6) undergoes a secondequalization falling step (EQ2DN) at the product end, by sending lowpressure equalization gas to bed 58 d (B8) (feed end) that is undergoingthe first equalization rising (EQ1UP) step.

During the adsorption (AD) steps, product that is not supply product gasto another bed undergoing product pressurization is being supplied tobuffer tank 64 and subsequently as product helium stream 40. The controlvalve shown in FIG. 8 can be used to control or moderate the flow ofhelium product stream 40. In addition, the tail gas from the four bedsis preferably recycled as stream 42 to the stage one VPSA system asdiscussed above via vacuum pump (VP) 84 and compressor 44. PV-3 and PV-4are process control valves that can control or modulate the flow of gasgoing in and out of the beds.

The valve switching logic for stage two of the four bed VPSA system andprocess (FIGS. 8 and 9) is shown in Table 5, and the duration of eachstep in the VPSA cycle as shown in Table 6. In particular, Table 5summarizes the valve sequence over one complete cycle for the four bedVPSA process shown in FIG. 8, and Table 6 gives the respective timeintervals and the corresponding status of each bed during one completeVPSA cycle. It can be seen from Tables 5 and 6 that the four bedsoperate in parallel, and during ¼ of the total cycle time one of thebeds is in the adsorption step, while the other beds are each undergoingone of the other steps as disclosed in the VPSA cycle.

Table 7 (Stage 2) gives an example of the operating conditions and theVPSA process performance using three layers of adsorbents (alumina,activated carbon, and zeolite), in each adsorber of the four bed VPSAprocess shown in FIG. 8. The first layer (layer 1 in FIG. 8) is 1.0 ftalumina, followed by 1.0 ft activated carbon (layer 2 in FIG. 8), then6.0 ft of VSA-6 zeolite. In the table, the symbols have the followingmeaning: kPa=1000 Pa=S.I. unit for pressure (1.0 atm.=101.323 kPa),s=time unit in seconds. The results shown in the table corresponds tothe case where the effluent from the stage one VPSA is used as the feedgas to the stage two VPSA process.

TABLE 5 Stage Two Four Bed VPSA Valve Switching (O = OPENED, C = CLOSED)Step 1 2 3 4 5 6 7 8 9 10 11 12 Bed 5 AD1 AD2/ AD3/ EQ1DN PPG EQ2DN BDPG EQ1UP EQ2UP PP1 PP2 (BD5) PP1 PP2 Bed 6 BD PG EQ1UP EQ2UP PP1 PP2 AD1AD2/ AD3/ EQ1DN PPG EQ2DN (BD6) PP1 PP2 Bed 7 EQ1DN PPG EQ2DN BD PGEQ1UP EQ2UP PP1 PP2 AD1 AD2/ AD3/ (BD7) PP1 PP2 Bed 8 EQ2UP PP1 PP2 AD1AD2/ AD3/ EQ1DN PPG EQ2DN BD PG EQ1UP (BD8) PP1 PP2 Valve No. V61 O O OC C C C C C C C C V62 C C C C C C O O O C C C V63 C C C C C C C C C O OO V64 C C C O O O C C C C C C V65 O O C O O C O O C O O C V66 C C C C CC O O C C C C V67 O O C C C C C C C C C C V68 C C C O O C C C C C C CV69 C C C C C C C C C O O C V70 C O O C O O C O O C O O V71 O O O C C CC C C C C C V72 C C C C C C O O O C C C V73 C C C C C C C C C O O O V74C C C O O O C C C C C C V75 C C C C O O C O C C C C V76 C O C C C C C CC C O O V77 C O O C O C C C C C C C V78 C C C C C C C O O C O C V79 C CC O C C C C C O O O V80 C C C O O O C C C O C C V81 O C C C C C O O O CC C V82 O O O C C C O C C C C C V83 C C C C C C C C O C C C V84 C C O CC C C C C C C C V85 C C C C C O C C C C C C V86 C C C C C C C C C C C OV87 O O O O O O O O O O O O

TABLE 6 Time Interval and Step Sequence of Stage 2 VPSA Cycle (FIG. 9)Step Time Number Interval (sec) BED #5 BED #6 BED #7 BED #8 1  0-25 AD1BD EQ1DN EQ2UP 2 25-65 AD2/PP1 PG PPG PP1 3 65-90 AD3/PP2 EQ1UP EQ2DNPP2 4  90-115 EQ1DN EQ2UP BD AD1 5 115-155 PPG PP1 PG AD2/PP1 6 155-180EQ2DN PP2 EQ1UP AD3/PP2 7 180-205 BD AD1 EQ2UP EQ1DN 8 205-245 PGAD2/PP1 PP1 PPG 9 245-270 EQ1UP AD3/PP2 PP2 EQ2DN 10 270-295 EQ2UP EQ1DNAD1 BD 11 295-335 PP1 PPG AD2/PP1 PG 12 335-360 PP2 EQ2DN AD3/PP2 EQ1UPAD1 = First Adsorption Step AD2/PP1 = Second Adsorption Step/Firstproduct pressurization AD3/PP2 = Third Adsorption Step/Second productpressurization EQ1DN = First Equalization Down or top-to-top bedequalization PPG = Provide Purge Gas EQ2DN = Second Equalization Down ortop-to-bottom bed equalization BD = Blowdown PG = Purge EQ1UP = FirstEqualization Up or top-to-bottom bed equalization EQ2UP = SecondEqualization Up or top-to-top bed equalization PP1 = First ProductPressurization PP2 = Second Product Pressurization

Table 7 (Stage 2 Four Bed VPSA Process Details):

An example of the operating conditions and the VPSA process performanceusing 1.0 ft of alumina (layer 1), 1.0 ft of activated carbon (layer 2),and 6.0 ft of VSA-6 zeolite (layer 3) in a layered bed four bed PSA orVPSA process of FIGS. 8 and 9 (Bed diameter=3.0 ft) is provided. Theresults shown below were obtained from VPSA simulation results using afeed mixture 90.04% He, 0.46% CO₂, 1.0% O₂ and 8.5% N₂.

Cycle time (s) 360 Adsorbent in first layer of Bed alumina Amount ofalumina (lb/bed): 340 Adsorbent in second layer of bed: activated carbonAmount of activated carbon (lb/bed): 222 Adsorbent in third layer ofbed: VSA-6 Amount of VSA6 zeolite (lb/bed): 1,753 High Pressure: 480 kPaLow Pressure: 60.96 kPa Feed Flowrate: 196.83 scfm Helium Purity:99.995% Stage 2 Per Pass Helium Recovery: 60% Stage 2 Tail Gas (Recycleto Stage 1 feed) 77.7% He Overall Two Stage He Recovery 95% Temperature:310 K

FIG. 10 shows a computer-simulated comparison of the two stage heliumrecovery process of the present invention using layered beds ofadsorbents and improved VPSA cycles versus prior art helium recoverycycles shown in U.S. Pat. No. 5,542,966 to D'Amico et al using activatedcarbon beds and the VPSA operating conditions and feed streams of thepresent invention (i.e. using the stage one conditions and feed streamnoted above in Table 4 and the stage two conditions and feed streamnoted above in Table 7). As is evident from FIG. 10, the helium recoveryprocess of the present invention is expected to have about 24% more Hethroughput (112 scfm vs 90 scfm) and about 10% improvement in Herecovery (95% vs. 86%).

FIG. 11 shows an alternative embodiment using a two stage VPSA systemwithout the upstream TSA system shown in FIG. 1. In this alternativemode of operation (FIG. 11), the VPSA stage one system is designed toremove the heavy contaminants (e.g. heavy hydrocarbons) that werepreviously taken out by the upstream TSA system of FIG. 1. Suchembodiments may be possible or desirable where the heavy contaminantsare capable of being removed in the VPSA system such that adsorbentregeneration of the stage one adsorbents is possible in an efficient oreconomic manner. For example and while not to be construed as limitingof the invention, it may be possible for silica gel adsorbent in thestage one VPSA system to remove a C6 hydrocarbon such as hexane whilesuch an adsorbent could not be efficiently regenerated throughdesorption if the C6+ hydrocarbon were BTX or the like instead ofhexane. When feed streams contain heavy contaminants that can be removedand the adsorbents efficiently regenerated, then the embodiment shown inFIG. 11 may be desirable. As can be seen from FIG. 11, feed 118 isintroduced into buffer tank 120 and then stream 122 fed to the VPSAstage one system 124. VPSA stage one system 124 produces waste gas 126and effluent 168. Effluent 168 is provided to stage one receiver 166 andis then fed to VPSA stage two system 138 as stream 170. VPSA stage twosystem 138 produces helium product stream 140 and waste tail gas 142,which can be recycled to the stage one VPSA system via recyclecompressor 144 as stream 146.

FIG. 12 shows an alternative embodiment using a modified version of FIG.11 for the case where the feed gas contains H2. In FIG. 12, a deoxo unit172 is added for the H2 removal prior to sending stage one effluent tothe stage two VPSA process. In a similar manner, the deoxo unit could beadded between stage one VPSA and stage two VPSA in FIG. 1 when H2 ispresent in the helium-containing feed gas. More specifically, stream 170from stage one receiver 166 and air stream 174 are introduced into deoxounit 172 to remove H2 to produce stream 176 depleted of hydrogen. Stream176 is then introduced into H2O removal unit 178 to produce water stream180 and a water deficient stream 182 going to the stage two VPSA system.

Depending on the kind of impurities and concentrations of componentspresent in the helium-containing feed gases (e.g., NH3, HCl, BTX, H2S,H2O, C1-C8 hydrocarbons, aromatics, etc), one layer or more than twolayers of adsorbents may be desired in each TSA bed of FIG. 3, and theTSA process could operate in TSA or VPSA or PSA modes. Several PSA andTSA cycles using two or more beds are disclosed in the prior art (e.g.,U.S. Pat. No. 4,233,038 to Tao; U.S. Pat. No. 5,614,000 to Kalbasi etal.; and U.S. Pat. No. 6,503,299 to Baksh et al.).

The teachings of the present invention can be utilized for other feedgases (e.g., H2-containing feed gases from refineries) containing heavycontaminants. Depending on the impurities present in the feed gas andthe choice of adsorbents, a PSA or TSA or combination of PSA/TSAprocesses may be desired or required to remove the impurities from thevarious off-gases. For example, the TSA process in FIGS. 3 and 4 couldbe a two bed temperature swing adsorption (TSA) process instead of thethree bed TSA process disclosed in FIGS. 3 and 4 and Table 1.Alternatively, the TSA process of FIGS. 3 and 4 could operate in TSA andPSA modes; i.e., different pressures and temperatures used during theonline steps versus the heating/cooling steps. By operating the TSAprocess at reduced pressure during the heating/cooling steps, improvedworking capacities of the adsorbents could be achieved in thepretreatment system.

Referring to FIGS. 1, 3 and 4, a combination of adsorbents can be usedin the TSA process when heavy components (e.g., H2S, C₃H₈, C4+, benzene,toluene, xylene, styrene, etc) are present in the helium-containing feedgas such as low grade natural gas. Alternative choices of adsorbents(e.g., layers S1 and S2) in FIGS. 2-4, include but are not limited to,the following: (A) wash coat of γ-Al2O3 (i.e. gamma alumina) and ZSM5zeolite onto honeycomb/monolithic ceramic or metallic substrates orstainless steel wire meshes (see, J. Chem. Eng. Data, V48, pg 1471,2003). The wash coat could include γ-Al2O3 (e.g., 80%) and ZSM5 zeolite(e.g., 20%). Other wash coats could be used for different heavycomponent impurities. In addition, the monolithic substrates composed ofsingle solid devices having many parallel channels that may be circular,hexagonal, square, triangular or sinusoidal are also expected to besuitable for use in the invention (see e.g. U.S. patent application Ser.No. 11/644,287 to Baksh, filed Dec. 22, 2006 and entitled “CompositeStructured Adsorbents” and published as U.S. Published PatentApplication No. US2008-0148936 A1 on Jun. 26, 2008 as well as PCTInternational Patent Application No. PCT/U.S.07/88598 entitled“Composite Structured Adsorbents”, filed Dec. 21, 2007 and published onJul. 3, 2008 as WO 2008/080080 A2; the entire contents of U.S. patentapplication Ser. No. 11/644,287 (and U.S. Published Patent ApplicationNo. US2008-0148936 A1) and PCT International Patent Application No.PCT/U.S.07/88598 are incorporated herein by reference). In addition, theparameters such as cell density, geometric surface area, void fraction,hydraulic diameter, void fraction of catalyst, characteristic diffusionlength, etc. can be defined for a given feed gas composition and PSA orVPSA operating conditions. (B) Pure silica Si-CHA {Diaz-Cabanas, et al.,Chem. Commun., (1998) 1881} or ITQ-3 {Olson et al., Microporous andMesoporous Materials 67 (2004) 27-33}, or high silica ZSM-58 (see U.S.Pat. No. 4,698,217). These adsorbents could also be used in theseparation of propane from a propene/propane mixture or for theseparation of ethane/ethene from higher hydrocarbons. (C) Sulfonatedstyrene/divinylbenzene resin (e.g., Ambersorb 600 from Rohm and HaasCo.). (D) HiSiv zeolites such as HiSiv 3000 from UOP. (E) Electricallyconductive activated carbon monolith (e.g., Joule heating to assist inadsorbent regeneration in the PSA cycle). This choice can facilitate theuse of higher desorption pressure and/or can eliminate the need forrecompressing the gas returning to the fuel head in the refineryprocess. (F) Silica gel and highly siliceous adsorbents such asdealuminated Y-type zeolite, ZSM zeolites, MCM-41, MCM-48, andsilicalite.

Depending on the types of impurities present in the helium-containingfeed gas, one or a combination of the aforementioned adsorbents could beused in the TSA/VPSA beds of the present invention. In addition,structured adsorbents are expected to be suitable for use in some or allof the beds in FIGS. 3, 6 and 8. See e.g. U.S. patent application Ser.No. 11/644,287 to Baksh, filed Dec. 22, 2006 and entitled “CompositeStructured Adsorbents” and published as U.S. Published PatentApplication No. US2008-0148936 A1 on Jun. 26, 2008 as well as PCTInternational Patent Application No. PCT/U.S.07/88598 entitled“Composite Structured Adsorbents”, filed Dec. 21, 2007 and published onJul. 3, 2008 as WO 2008/080080 A2; the entire contents of U.S. patentapplication Ser. No. 11/644,287 (and U.S. Published Patent ApplicationNo. US2008-0148936 A1) and PCT International Patent Application No.PCT/U.S.07/88598 are incorporated herein by reference.

Although the aforementioned invention is disclosed with respect to theproduction of helium from low helium-containing feed gases, variouschanges or modifications could be made, by one ordinarily skilled in theart, without departing from the scope of the present invention.Additionally, more or less number of beds could be used in the processof FIGS. 3, 6 and 8. Moreover, each bed could include one or severallayers of adsorbents, or mixtures of adsorbents. The adsorberconfiguration selected (e.g., radial, axial, structured, etc) and choiceand arrangement of the adsorbents will be determined based on size ofthe feed flow, the type of feed source, and TSA/VPSA process operatingconditions.

In addition, CaX, VSA-6, 5A, 13X, and mixed cations zeolites could beused as the adsorbents in the VPSA processes of FIGS. 6 and 8. Otheradsorbents, including activated carbons with different bulk densitiesand other zeolitic materials such as Li—X zeolite, CaX(2.0), etc, couldfurther be used in the VPSA separation process without deviating fromthe scope of the invention. For example, instead of using (or, inaddition to using) VSA-6 zeolite, the VPSA process could also use CaX(2.0), naturally occurring crystalline zeolite molecular sieves such aschabazite, erionite and faujasite and combinations thereof. In addition,zeolite containing lithium/alkaline earth metal A and X zeolites (seeU.S. Pat. Nos. 5,413,625 and 5,174,979 to Chao et al.; and U.S. Pat.Nos. 5,698,013; 5,454,857 and 4,859,217 to Chao) may also be suitablefor use in the present invention.

Additionally, each of the layered adsorbent zones in each of the VPSAbed in FIGS. 6 and 8 could be replaced with layers of adsorbents. Forexample, the single layer of zeolite in each bed could be replaced withmultiple layers of different adsorbents (e.g., VSA 6 could be replacedby a first layer of 13 X with VSA6 on top). In addition, the zeolitelayer could be substituted by a composite adsorbent layer containingdifferent adsorbent materials positioned in separate zones in whichtemperature conditions within a bed favor adsorption performance of theparticular adsorbent material under applicable processing conditions ineach zone. Further details on composite adsorbent layer design aredisclosed for example in U.S. Pat. No. 5,674,311 by Notaro et al.

It will be appreciated by those skilled in the art that the time for agiven cycle or phase in a given cycle can vary depending on severalfactors, such as the composition of the feed (including theconcentrations of the impurities therein), process conditions such asflow rates and pressures and size of adsorbent beds. It will further beappreciated by those skilled in the art that cycle and phase times canbe selected depending on the time it takes for an adsorbent bed to reachbreakthrough conditions. In addition, appropriate valves can be selectedbased on the desired function(s). It should be appreciated thatcontrolled scheme and apparatus for controlling the desired productpurity and the various operating conditions associated with each systemare incorporated in the recovery process via computer programming andinterface.

Although the aforementioned invention is disclosed in relation to heliumrecovery from low helium (i.e., less than 10% helium byvolume)-containing feed gases, the aforementioned key features couldalso be extended to other separation/purification processes, such as forexample the recovery of hydrogen from refinery off gases. In such cases,the % of hydrogen in the feed gas may be in the range of 20-75% hydrogenby volume.

Although the invention has been described in detail with reference tocertain preferred embodiments, those skilled in the art will recognizethat there are other embodiments within the spirit and the scope of theclaims.

1. A process for the recovery of helium, the process comprising:introducing a helium-containing feed gas into a temperature swingadsorption system; pretreating the helium-containing feed gas in thetemperature swing adsorption system to produce a helium-containingpretreated feed gas; treating the helium-containing pretreated feed gasin a stage one pressure swing adsorption system to produce a stage onehelium-containing purified gas and a stage one tail gas; and treatingthe helium-containing purified gas in a stage two pressure swingadsorption system to produce a helium-containing product stream and astage two tail gas, wherein at least a portion of the stage one tail gasis introduced into the temperature swing adsorption system.
 2. Thehelium recovery process of claim 1, wherein at least a portion of thestage two tail gas is introduced into the stage one pressure swingadsorption system.
 3. The helium recovery process of claim 1, furthercomprising feeding at least a portion of the stage one tail gas into afirst buffer tank and providing at least a portion of the stage one tailgas from the first buffer tank to the temperature swing adsorptionsystem.
 4. The helium recovery process of claim 1, further comprisingfeeding the helium-containing pretreated feed gas into a second buffertank and providing the helium-containing pretreated feed gas from thesecond buffer tank to the stage one pressure swing adsorption system andfurther comprising feeding the helium-containing purified feed gas to athird buffer tank and providing the helium-containing purified feed gasfrom the third buffer tank to the stage two pressure swing adsorptionsystem.
 5. The helium recovery process of claim 1, wherein the stage onepressure swing adsorption system comprises a vacuum pressure swingadsorption (VPSA) system.
 6. The helium recovery process of claim 5,wherein the stage one VPSA system includes four adsorption beds, eachadsorption bed having at least one adsorbent contained therein.
 7. Thehelium recovery process of claim 6, wherein each adsorbent bed in thestage one VPSA system includes at least a first adsorbent, a secondadsorbent and a third adsorbent contained therein.
 8. The heliumrecovery process of claim 7, wherein the first adsorbent in the stageone VPSA system comprises alumina contained proximate to a first end ofeach respective adsorbent bed, the second adsorbent in the stage oneVPSA system comprises activated carbon positioned downstream of thealumina adsorbent in each respective bed and the third adsorbent in thestage one VPSA system comprises zeolite positioned downstream of theactivated carbon adsorbent in each respective bed.
 9. The heliumrecovery process of claim 6, wherein the helium-containing pretreatedgas is processed in the stage one VPSA system to produce thehelium-containing purified feed gas in a twelve-step cycle in which:Step 1 2 3 4 5 6 7 8 9 10 11 12 Bed 1 AD1 AD2/ AD3/ EQ1DN PPG EQ2DN BDPG EQ1UP EQ2UP PP1 PP2 (BD1) PP1 PP2 Bed 2 BD PG EQ1UP EQ2UP PP1 PP2 AD1AD2/ AD3/ EQ1DN PPG EQ2DN (BD2) PP1 PP2 Bed 3 EQ1DN PPG EQ2DN BD PGEQ1UP EQ2UP PP1 PP2 AD1 AD2/ AD3/ (BD3) PP1 PP2 Bed 4 EQ2UP PP1 PP2 AD1AD2/ AD3/ EQ1DN PPG EQ2DN BD PG EQ1UP (BD4) PP1 PP2 wherein AD1 = FirstAdsorption Step AD2/PP1 = Second Adsorption Step/First productpressurization AD3/PP2 = Third Adsorption Step/Second productpressurization EQ1DN = First Equalization Down or top-to-top bedequalization PPG = Provide Purge Gas EQ2DN = Second Equalization Down orbottom-to-bottom bed equalization BD = Blowdown PG = Purge EQ1UP = FirstEqualization Up or bottom-to-bottom bed equalization EQ2UP = SecondEqualization Up or top-to-top bed equalization PP1 = First ProductPressurization PP2 = Second Product Pressurization


10. The helium recovery process of claim 1, wherein the stage twopressure swing adsorption system comprises a vacuum pressure swingadsorption (VPSA) system.
 11. The helium recovery process of claim 10,wherein the stage two VPSA system includes four adsorption beds, eachadsorption bed having at least one adsorbent contained therein.
 12. Thehelium recovery process of claim 11, wherein each adsorbent bed in thestage two VPSA system includes at least a first adsorbent, a secondadsorbent and a third adsorbent contained therein.
 13. The heliumrecovery process of claim 12, wherein the first adsorbent in the stagetwo VPSA system comprises alumina contained proximate to a first end ofeach respective adsorbent bed, the second adsorbent in the stage twoVPSA system comprises activated carbon positioned downstream of thealumina adsorbent in each respective bed and the third adsorbent in thestage two VPSA system comprises zeolite positioned downstream of theactivated carbon adsorbent in each respective bed.
 14. The heliumrecovery process of claim 11, wherein the helium-containing purified gasis processed in the stage two VPSA system to produce thehelium-containing product feed gas in a twelve-step cycle in which: Step1 2 3 4 5 6 7 8 9 10 11 12 Bed 1 AD1 AD2/ AD3/ EQ1DN PPG EQ2DN BD PGEQ1UP EQ2UP PP1 PP2 (BD1) PP1 PP2 Bed 2 BD PG EQ1UP EQ2UP PP1 PP2 AD1AD2/ AD3/ EQ1DN PPG EQ2DN (BD2) PP1 PP2 Bed 3 EQ1DN PPG EQ2DN BD PGEQ1UP EQ2UP PP1 PP2 AD1 AD2/ AD3/ (BD3) PP1 PP2 Bed 4 EQ2UP PP1 PP2 AD1AD2/ AD3/ EQ1DN PPG EQ2DN BD PG EQ1UP (BD4) PP1 PP2 wherein AD1 = FirstAdsorption Step AD2/PP1 = Second Adsorption Step/First productpressurization AD3/PP2 = Third Adsorption Step/Second productpressurization EQ1DN = First Equalization Down or top-to-top bedequalization PPG = Provide Purge Gas EQ2DN = Second Equalization Down ortop-to-bottom bed equalization BD = Blowdown PG = Purge EQ1UP = FirstEqualization Up or top-to-bottom bed equalization EQ2UP = SecondEqualization Up or top-to-top bed equalization PP1 = First ProductPressurization PP2 = Second Product Pressurization


15. The helium recovery process of claim 1, wherein the temperatureswing adsorption system includes three adsorption beds, each adsorptionbed having at least one adsorbent contained therein.
 16. The heliumrecovery process of claim 15, wherein the at least one adsorbentselectively adsorbs at least one heavy contaminant in thehelium-containing feed gas.
 17. The helium recovery system of claim 16,wherein the at least one heavy contaminant in the helium-containing feedgas is selected from the group comprising: C₆ ⁺ heavy hydrocarbons, H₂S,H₂O and mixtures thereof.
 18. The helium recovery process of claim 15,wherein the helium-containing feed gas is processed in the temperatureswing adsorption system to produce the helium-containing pretreated feedgas in a three-step cycle in which: Step 1 2 3 Bed No. 1 Online HeatingCooling (PB1) Bed No. 2 Cooling Online Heating (PB2) Bed No. 3 HeatingCooling Online (PB3)

wherein Online is adsorption step, Heating is counter-current withrespect to feed direction, and Cooling is co-current with respect tofeed direction.
 19. The helium recovery process of claim 15, whereineach adsorbent bed includes at least a first adsorbent and a secondadsorbent contained therein.
 20. The helium recovery process of claim19, wherein the first adsorbent comprises alumina and the secondadsorbent comprises at least one adsorbent selected from the groupcomprising: silica gel, titanium silicates, aluminosilicates, ZSM5supported on gamma alumina, alumina, activated carbon and treatedactivated carbon and clinoptilolite.
 21. The helium recovery process ofclaim 20, wherein the first adsorbent comprises alumina and the secondadsorbent comprises barium ion exchanged clinoptilolite.
 22. A processfor the recovery of helium, the process comprising: treating ahelium-containing feed gas in a stage one pressure swing adsorptionsystem comprising four adsorption beds (Bed 1 (BD1), Bed 2 (BD2), Bed 3(BD3), Bed 4 (BD4)) to produce a stage one helium-containing purifiedfeed gas and a stage one tail gas; and treating the helium-containingpurified feed gas in a stage two pressure swing adsorption systemcomprising four adsorption beds (Bed 5 (BD5), Bed 6 (BD6), Bed 7 (BD7),Bed 8 (BD8)) to produce a helium-containing product stream and a stagetwo tail gas, wherein the stage one VPSA system to produce thehelium-containing purified feed gas comprises a twelve-step cycle inwhich: Step 1 2 3 4 5 6 7 8 9 10 11 12 Bed 1 AD1 AD2/ AD3/ EQ1DN PPGEQ2DN BD PG EQ1UP EQ2UP PP1 PP2 (BD1) PP1 PP2 Bed 2 BD PG EQ1UP EQ2UPPP1 PP2 AD1 AD2/ AD3/ EQ1DN PPG EQ2DN (BD2) PP1 PP2 Bed 3 EQ1DN PPGEQ2DN BD PG EQ1UP EQ2UP PP1 PP2 AD1 AD2/ AD3/ (BD3) PP1 PP2 Bed 4 EQ2UPPP1 PP2 AD1 AD2/ AD3/ EQ1DN PPG EQ2DN BD PG EQ1UP (BD4) PP1 PP2 whereinAD1 = First Adsorption Step AD2/PP1 = Second Adsorption Step/Firstproduct pressurization AD3/PP2 = Third Adsorption Step/Second productpressurization EQ1DN = First Equalization Down or top-to-top bedequalization PPG = Provide Purge Gas EQ2DN = Second Equalization Down orbottom-to-bottom bed equalization BD = Blowdown PG = Purge EQ1UP = FirstEqualization Up or bottom-to-bottom bed equalization EQ2UP = SecondEqualization Up or top-to-top bed equalization PP1 = First ProductPressurization PP2 = Second Product Pressurization,

and wherein the helium-containing purified gas is processed in the stagetwo VPSA system to produce the helium-containing product feed gascomprises a twelve-step cycle in which: Step 1 2 3 4 5 6 7 8 9 10 11 12Bed 5 AD1 AD2/ AD3/ EQ1DN PPG EQ2DN BD PG EQ1UP EQ2UP PP1 PP2 (BD5) PP1PP2 Bed 6 BD PG EQ1UP EQ2UP PP1 PP2 AD1 AD2/ AD3/ EQ1DN PPG EQ2DN (BD6)PP1 PP2 Bed 7 EQ1DN PPG EQ2DN BD PG EQ1UP EQ2UP PP1 PP2 AD1 AD2/ AD3/(BD7) PP1 PP2 Bed 8 EQ2UP PP1 PP2 AD1 AD2/ AD3/ EQ1DN PPG EQ2DN BD PGEQ1UP (BD8) PP1 PP2 wherein AD1 = First Adsorption Step AD2/PP1 = SecondAdsorption Step/First product pressurization AD3/PP2 = Third AdsorptionStep/Second product pressurization EQ1DN = First Equalization Down ortop-to-top bed equalization PPG = Provide Purge Gas EQ2DN = SecondEqualization Down or top-to-bottom bed equalization BD = Blowdown PG =Purge EQ1UP = First Equalization Up or top-to-bottom bed equalizationEQ2UP = Second Equalization Up or top-to-top bed equalization PP1 =First Product Pressurization PP2 = Second Product Pressurization.


23. A system for hydrogen recovery, the system comprising: a temperatureswing adsorption system configured to receive a hydrogen-containing feedgas and configured to produce a hydrogen-containing pretreated feed gas;a stage one pressure swing adsorption system configured to receive thehydrogen-containing pretreated feed gas and configured to produce astage one hydrogen-containing purified feed gas and a stage one tailgas; and a stage two pressure swing adsorption system configured toreceive the stage one hydrogen-containing purified feed gas andconfigured to produce a hydrogen-containing product stream and a stagetwo tail gas, wherein the temperature swing adsorption system is furtherconfigured to receive at least a portion of the stage one tail gas.